Senator Mitch McConnell warned Democrats on Thursday against killing the legislative-filibuster rule, the Senate’s 60-vote threshold for shutting down debate on a piece of legislation.

“The legislative filibuster is directly downstream from our founding tradition. If that tradition frustrates the whims of those on the far left, it is their half-baked proposals and not the centuries-old wisdom that need retooling,” McConnell wrote in a New York Timesop-ed published Thursday.

McConnell recalled warning then-Senate majority leader Harry Reid in November 2013 against the “nuclear option” of altering Senate rules in order to prevent members of the minority party from filibustering non-Supreme Court nominees.

“You’ll regret this, and you may regret this a lot sooner than you think,” the Kentucky Republican said on the Senate floor at the time.

“No Republican has any trouble imagining the laundry list of socialist policies that 51 Senate Democrats would happily inflict on Middle America in a filibuster-free Senate,” McConnell wrote Thursday.

“Unfortunately, Senate Democrats bought what Senator Reid was selling — but buyer’s remorse arrived with lightning speed,” McConnell continued. “In 2017, we took the Reid precedent to its logical conclusion, covering all nominations up to and including the Supreme Court.”

Senate minority leader Charles Schumer and Senator Elizabeth Warren, who is polling second in the race for the Democratic presidential nomination, have both expressed support for eliminating the filibuster rule.

“I hope the saner voices among Democrats can help their compatriots see reason,” McConnell said. “If future Democrats shortsightedly decide to reduce the Senate to majority rule, we’ll have lost a key safeguard of American government.”